observe vs undersee

observe

verb
  • To notice or view, especially carefully or with attention to detail. 

  • To take note of and celebrate (a holiday or similar occurrence); to follow (a type of time or calendar reckoning). 

  • To comment on something; to make an observation. 

  • To follow or obey the custom, practice, or rules (especially of a religion). 

undersee

verb
  • To look intently into; examine; inspect. 

  • To see or look under or below; see below the surface of. 

  • To neglect; fail to see properly or adequately; turn a blind eye to; ignore. 

How often have the words observe and undersee occurred in a corpus of books? (source: Google Ngram Viewer )